1. Field of the Invention
This invention relates to a reusable fitment attached to an end portion of an optical fiber for connecting the optical fiber to a light source.
2. Description of Related Art
The optical fiber consists of a core made of a translucent material having a high refractive index and a clad made of a material having a refractive index lower than that of the core, and is used in various applications for optical transmission such as optical communication, illumination and the like.
In general, a solid material or liquid material is used as the core for the optical fiber. And also, a core having a large diameter of not less than 3 mm may be used for efficiently transmitting a greater quantity of a light. Furthermore, a bundle of many optical fibers each having a fine diameter of about 1 mm (bundle fiber) is frequently used.
In this case, it is preferable to use a solid core as the core for the optical fiber because of the handling easiness that the optical fiber can be cut into a required length at an installation location in use. Particularly, the use of a single core made of a plastic material is more favorable because it has a flexibility and facilitates the installation work.
In this type of the optical fiber, a light is directly entered from a light source through an end face of the solid core into an inside of the optical fiber and emitted from the other end face of the core after the propagation through the inside of the core. Since it is general to use the core by cutting into the required length, the cut end face of the core usually has microscopic irregularities, so that it tends to decrease an incident efficiency of the light. Even if the cut end face is rendered into a smooth face by polishing, since the polished end face is directly exposed to external environment, it is liable to adhere contaminants existing in the environment such as dusts and the like to the polished end face. When the light from the light source is directly irradiated to the end face of the core at a state of adhering the contaminants thereto, the incident efficiency of the irradiated light lowers and also a part of the light irradiated to the end face of the core is absorbed by the core to convert into heat and hence the end face of the core tends to generate heat.
And also, since a light source apparatus for the optical fiber i is high in the light energy at a light condensed portion to the optical fiber, if the end face of the optical fiber is directly disposed opposite to the light condensed portion, it is naturally rendered into a high temperature by heating, and consequently the core is apt to create thermal expansion, softening or thermal deterioration, and in the worst case, it is fear to bring about a fire by beginning to burn from the end face of the core.
Furthermore,.when the end face of the core is exposed to the external environment, there is a case that water in moisture existing in the external environment adheres to the end face of the core, which results in the occurrence of whitening phenomenon at the end face to bring about the lowering of light transmission efficiency.
For this end, there have been made various studies for solving the above problems, and a solution is disclosed, for example, in JP-A-8-313,739.
As shown in FIG. 4, an optical fiber 23 disclosed in the above publication consists of a core 21 and a clad 22, wherein a translucent window member 25 is fixed to at least an end face 24 of the core 21 at its light entrance side with an adhesive 26 and each end portion of the clad 22 is secured to respective end portion of the core 21 by placing a fitting member 27 on an outer peripheral surface of each end portion of the clad 22 and caulking it.
In such an optical fiber 23, the end face 24 at the light entrance side is shut off from the external environment through the translucent window member 25, so that the adhesion of contaminants, water and the like to the end face 24 can be prevented and hence the lowering of the light transmission efficiency and the heat generation at the end face 24 resulted from this adhesion can effectively be controlled.
However, the fitting member 27 is caulked from exterior at the light entrance-side end portion of the optical fiber 23, so that a spot input by caulking acts on the core 21 through the clad 22 to thereby cause such a deformation that strain is locally caused in the core 21 and hence it tends to lower the light transmission efficiency.
And also, since a caulked portion between the fitting member 27 and the end portion of the optical fiber 23 is located at a side approaching to the light source, it is easily subjected to heat energy from the light source to create a difference in thermal expansion between the fitting member 27 and the optical fiber 23 in the caulked portion, and hence it tends to easily come out the optical fiber 23 from the fitting member 27 at the caulked portion.
Furthermore, when the fitting member 27 is fitted onto the optical fiber 23, it is required to use a special caulking device, which is not preferable from a viewpoint of the operability. In addition, the fitting member 27 is used at a caulked state to the optical fiber 23, so that when the fitting member 27 is taken off from the optical fiber 23 and fitted onto another optical fiber, a considerable labor is taken. Moreover, since plastic deformation is caused in the caulked fitting member 27, the reuse of such a fitting member 27 is not favorable in case that it is necessary to surely connect the fitting member 27 to the optical fiber 23.
It is, therefore, an object of the invention to provide a reusable fitment wherein a translucent window member is fixed to an inside of a top of a main body of the fitment to shut off an end face of an optical fiber from external environment to thereby prevent heat generation and an occurrence of whitening phenomenon at the end face, and the connection between the optical fiber and the fitment is carried out by an adequate connecting means hardly producing strain in a core of the optical fiber, and a connecting portion is arranged at a position separated from the end face of the optical fiber being subjected to a high temperature by irradiation of a light, whereby optical transmission loss due to thermal deformation at the connected portion is decreased and the fitment can be attached to or detached from the optical fiber in a short time and the good connected state to the optical fiber can be maintained over a long time.
According to the invention, there is the provision of a reusable fitment comprising a cylindrical main body having an inner diameter substantially equal to an outer diameter of an optical fiber, a translucent window member fixed to an inside of at least a top portion of the main body, and a connector detachably connected to a rear end portion of the main body for fixing and holding the optical fiber.
In case of requiring that an incident light is perfectly reflected at an outer peripheral surface of the translucent window member to more efficiently transmit to the optical fiber, it is favorable to cover the outer peripheral surface of the translucent window member with a coating layer having a refractive index lower than that of the window member.
Furthermore, it is favorable that the translucent window member is fixed to the main body of the fitment by fitting the window member into the top portion of the main body and caulking the main body from an outer surface thereof, or by using an adhesive, or by utilizing both means.
Moreover, it is favorable that the optical fiber is a single-core type optical fiber having a large diameter.